The present invention is directed to a stuffer box crimping apparatus for crimping continuous filament tow for textile and industrial yarn purposes, and is particularly directed to an improved supporting arrangement for the moveable ribbon sideplates in the stuffer box crimping apparatus disclosed in U.S. Pat. No. 3,353,223, which issued Nov. 21, 1967.
Stuffer box crimping involves continuously feeding filament tow through the nip of a pair of coacting feedrolls into a crimping chamber, which may or may not be heated and which has some type of arrangement for adjusting the back pressure upon the tow in the crimping chamber, such as a clapper gate arrangement.
The tow is fed through the nip of the coacting feedrolls into the crimping chamber against the tow that is being held in the crimping chamber by the clapper gate arrangement. The incoming tow thus piles up against the chamber tow with the result that individual filaments become folded, convoluted and compressed. This continues until at some point in time, dependent upon feed rate, chamber geometry, and the extent of back pressure, crimped tow is forced out the discharge opening of the crimping chamber by other incoming tow.
The continuous filament tow may be made from any of the man-made fibers, such as from cellulose esters, polyesters, polyamides and the like. In the use of polyester, for instance, a white color may be imparted to the tow by use of a pigment such as titanium dioxide (TiO.sub.2), which causes the tow to have an abrasive wearing effect on the crimping chamber, particularly with respect to the sideplates. The sideplates can become so worn as to cause poorly formed edges on the tow passing through the crimping chamber and even tearing and breaking of the filaments that come into contact with the worn sideplates. The above-mentioned U.S. Pat. No. 3,353,223 disclosed a solution for the problem of worn sideplates by providing a substantially uniform renewable surface against which tow to be crimped may bear as it passes through the crimping chamber. The disclosed renewable surface is in the form of a moveable ribbon sideplate, which may be made from a suitable material, such as brass, for instance, and which may be intermittently moved through the crimping chamber or moved continuously at a rate that will preclude undue wear of the ribbon sideplates by the abrasive tow. The ribbon sideplates, for instance, may be introduced from a supply roll located externally of the crimping chamber.
As shown in U.S. Pat. No. 3,353,223, each ribbon sideplate moves from a supply roll along the endfaces of the feedrolls and along one of the sidewalls of the crimping chamber. The ribbon sideplate is caused to bear closely against the endfaces of the feedrolls in sealing relation by a back-up pressure plate, which is adjustably loaded against the ribbon sideplate by adjusting screws and lock nuts mounted in a pressure plate holder. The ribbon sideplate serves to define one of the sidewalls of the crimping chamber and to prevent filaments of the tow from escaping past the ribbon sideplate at the feedroll endfaces. The top and bottom of the crimper chamber are formed by scraper blades, which nearly touch the surfaces, respectively, of the upper and lower feedrolls. The ribbon sideplate also forms a sealing relation with the upper and lower scraper blades to confine the tow within the crimping chamber.
One problem noted in the use of the ribbon sideplates concerns the effect of the adjustment of the ribbon sideplate against the endfaces of the feedrolls. Since the ribbon sideplate is relatively thin and flexible, it is forced by the pressure within the stuffing box chamber to conform to the shape of the surfaces which support it. A back-up pressure plate is located opposite the endfaces of the feedrolls on each end of the feedrolls, and a ribbon sideplate is interposed between the back-up pressure plate and the endfaces of the feedrolls and is adjustably urged against the feedroll endfaces by the back-up pressure plate. Where the ribbon sideplate extends past the feedroll endfaces and the back-up pressure plate and into the crimping chamber, an offset is created between the end of the back-up pressure plate and the adjacent sidewall. Because of the above-mentioned pressure within the stuffing box chamber, the ribbon sideplate conforms to this offset with the result that a kink is formed in its surface. Also, the endfaces of the feedrolls are gradually worn away during operation as they rub against the ribbon sideplates. Therefore, the back-up pressure plate has to be manually adjusted toward the feedrolls periodically so as to maintain the sealing relation. This results in a greater offset between the surface of the back-up pressure plate and the adjacent sidewall of the crimping chamber. When the ribbon sideplate is moved relative to the feedroll endfaces and sidewalls of the crimping chamber, the kink causes the ribbon sideplate to hang, sometimes causing the ribbon to be pulled apart, or causing a rough section of ribbon sideplate to be exposed to the tow. This produces a ragged edge on the crimped tow, and the operator anticipating this poor effect moves the ribbon sideplate more than would otherwise be required in order to remove the kinked ribbon sideplate from contact with the tow or the feedrolls, thus wasting expensive ribbon sideplates. Also, a ragged edge is produced on the tow while the kink is being moved between the back-up pressure plate and the roll feedroll endfaces.
Attempts have been made to alleviate the problem by making ribbon sideplates of increasing greater thicknesses, but this only makes the ribbon sideplate more expensive to manufacture without actually eliminating the potential for the ribbon sideplate to become kinked as the feedroll endfaces became more worn over a period of operating time. Also, attempts were made to change pressure back-up plate design, but this also did not serve to solve the problem.